Adhesion promoter composition and adherent rubber composition containing the same

ABSTRACT

An adhesion promoter composition containing a Zn, K, Al, Ti or Zr metal salt of an organic acid and at least one of a hydrous inorganic salt and an organic molybdenum compound. The adhesion promoter composition may be used to form an adherent rubber composition. The use of the adhesion promoter composition results in an adherent rubber composition which is stable and has a high adhesive force.

This application is filed under 35U.S.C. 371 claiming priority to PCT/JP 97/022A filed Jun. 26, 1997.

FIELD OF THE INVENTION

This invention relates to an adhesion promoter composition and an adherent rubber composition containing the adhesion promoter composition. More particularly the invention relates to (1) an adhesion promoter composition suitable for promoting the adhesion between brass plated steel cord and a rubber composition for coating the steel cord (hereinafter "coating rubber") and (2) an adherent rubber composition containing the adhesion promoter composition.

BACKGROUND OF THE INVENTION

In order to improve performances of automobile tires, conveyor belts and the like, steel cords are generally used as a reinforcing member.

Such steel cords are subjected to a brass plating in order to increase their adhesion to rubber (hereinafter "adhesive force") which thereby enhances their reinforcing effect.

On the other hand, a cobalt salt of an organic acid may be compounded as an adhesion promoter in a rubber composition in order to increase the adhesive force between rubber and steel cord.

However, the use of cobalt is not desirable for safety concerns and due to its high cost. And also, in case of using a cobalt salt of an organic acid, the adhesion property just after vulcanization is excellent, but the adhesion property after thermal aging is poor.

When the other metal salts of organic acids are compounded instead of the cobalt salt of the organic acid, the adhesive force just after vulcanization is poor. Therefore, metal salts of organic acids have not yet been put into practical use as a replacement for cobalt salts.

SUMMARY OF INVENTION

An object of the invention is to provide an adhesion promoter composition being advantageous in safety and economy and having a stably high adhesive force, and an adherent rubber composition containing the adhesion promoter composition.

In order to achieve the above object, the adhesion promoter composition according to the present invention is characterized as follows.

(1) Including a metal salt of an organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and a hydrous inorganic salt.

(2) Including a metal salt of an organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and an organic molybdenum compound.

(3) In addition to the components of the adhesion promoter composition according to the above item (1), an organic molybdenum compound is further included.

(4) In the adhesion promoter composition according to the above items (1) or (3), a molar ratio (H₂ O /Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100.

(5) In the adhesion promoter composition according to the above items (2) or (3), a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100.

(6) In the adhesion promoter composition according to the above item (3), a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100, and a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100, and a molar ratio (H₂ O/Mo) of water (H₂ O) in the hydrous inorganic salt to molybdenum (Mo) in the organic molybdenum compound is 1-500.

Furthermore, the adherent rubber composition according to the invention is constructed as follows.

(7) Compounding a) at least one rubber ingredient selected from the group consisting of natural rubber and synthetic rubbers, b) an adhesion promoter composition described in any one of the above items (1)-(6), and c) sulfur.

(8) In the adherent rubber composition according to the above item (7), the adhesion promoter composition described in the above item (1) or (4) is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.5×10⁻³ -2.5×10⁻¹ mole calculated in terms of water in the hydrous inorganic salt, and sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient.

(9) In the adherent rubber composition according to the above item (7), the adhesion promoter composition described in the above item (2) or (5) is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.0×10⁻⁶ -2.0×10 mole calculated in terms of molybdenum in the molybdenum compound, and sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient.

(10) In the adherent rubber composition according to the above item (7), the adhesion promoter composition described in the above item (3) or (6) is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.5×10⁻³ -2.5×10⁻¹ mole calculated in terms of water in the hydrous inorganic salt and in an amount of 2.0×10⁻⁶ -2.0×10 mole calculated in terms of molybdenum in the molybdenum compound, and sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient.

The present invention is described in further detail below.

[1] The adhesion promoter composition according to the present invention is as follows.

a) The organic acid constituting the metal salt of organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr is not particularly restricted, and may be saturated or unsaturated, and have a straight or branched chain. Also, it may be a bulky fatty acid having a naphthene ring, a benzene ring or the like. Specific examples of organic acid include neodecanoic acid, stearic acid, naphthenic acid, rosin, tall oil acid, oleic acid, linoleic acid, linolenic acid and the like. Further, a part of the organic acid may be substituted with a boron-containing compound, such as boric acid or the like when the metal is multivalent.

Furthermore, the metal constituting the metal salt of organic acid according to the present invention is Zn, K, Al, Ti or Zr. Said metals are advantageous in safety, cost and the like.

Moreover, the metal salts of the organic acid include a plurality of same or different kind of metals being bonded in one molecule, and may be used alone or in a combination thereof.

b) The form of the organic molybdenum compound is not particularly limited, and includes an organic molybdenum sulfur compound having phosphorus or nitrogen such as molybdenum dithiophosphate (Mo-DTP), molybdenum dithiocarbaznate or the like, a molybdenum salt of an organic acid and the like. As the organic acid, the above-mentioned organic acids may be used.

Furthermore, when the metal salt of the organic acid and the organic molybdenum compound are included as components of the adhesion promoter composition, it is allowed to take a state of bonding at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and molybdenum together in one molecule.

c) As the hydrous inorganic salt, NiSO₄.7H₂ O, CoSO₄.7H₂ O, NaSO₄.10H₂ O, CaSO₄.2H₂ O, CuSO₄.5H₂ O, Al₂ (SO₄)₃.18H₂ O, FeSO₄ 7H₂ O, ZnSO₄.7H₂ O, MgSO₄.7H₂ O, Na₂ S.9H₂ O, Na₃ PO₄.12H₂ O, NaH₂ PO₄.2H₂ O, Na₂ HPO₄.12H₂ O, Ni₃ (PO₄)₂ 8H₂), Mg₃ (PO₄)₂.8H₂ O, Li₃ PO₄.5H₂ O, Na₄ P₂ O₇.10H₂ O, Ni₂ P₂ O₇.6H₂ O, Mn₄ (P₂ O₇)₃.14H₂, CoCO₃.6H₂ O, NiCO₃.6H₂ O, Na₂ CO₃ 10H₂ O, Nd₂ (CO₃)₃.8H₂ O, Na₂ SO₃.7H₂ O, CaCl₂.6H₂ O, NiCl₂.6H₂ O, Na₂ B₄ O₇.10H₂ O, FeCl₃ 6H₂ O, Na₂ SiO₃.9H₂ O and the like may be used. By compounding such a hydrous inorganic salt, H₂ O contained therein is released, whereby water content may be maintained even when a synthetic rubber having a low water content is compounded or in the winter season of drying air, and hence the lowering of the adhesive force can be avoided. Further, the adhesive force just after vulcanization i.e. an initial adhesive force may be improved.

It is preferable that when the metal salt of the organic acid and the hydrous inorganic salt are included as the ingredients of the adhesion promoter composition, the molar ratio (H₂ O /Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100. When the molar ratio is less than 0.1, the desired effect may not be obtained, while when it exceeds 100, the water content becomes too large and the adhesion property may be degraded.

Additionally, for the same reasons, the molar ratio is preferably 1-50, more preferably 5-20.

Furthermore, it is preferable that when the metal salt of the organic acid and the organic molybdenum compound are included as the ingredients of the adhesion promoter composition, the molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100. When the molar ratio is less than 0.01, the effect of compounding the organic molybdenum compound is not obtained, while when it exceeds 100, the cost is increased so as to be undesirable from an economical viewpoint, even though the effect is unchanged.

Additionally, for the same reasons, the molar ratio is preferably 0.03-10, more preferably 0.05-1.0.

Moreover, it is preferable that when the hydrous inorganic salt and the organic molybdenum compound are included as the ingredients of the adhesion promoter composition, the molar ratio (H₂ /MO) of water (H₂ O) in the hydrous inorganic salt to molybdenum (Mo) in the organic molybdenum compound is 1-500. When the molar ratio is outside this range, the synergistic effect is not obtained.

Additionally, for the same reasons, the molar ratio is preferably 10-100, more preferably 25-75.

[2] The adherent rubber composition according to the present invention is as follows.

As the rubber ingredient, at least one rubber is selected from natural rubber and synthetic rubbers. The synthetic rubber may be made of styrene-butadiene rubber (SBR), butadiene rubber, butyl rubber, halogenated butyl rubbers, preferably brominated butyl rubber, and butyl rubber having paramethylstyrene group (such as copolymer of isobutylene and p-halogenated methylstyrene, or the like), ethylene-propylene-diene rubber (EPDM), isoprene rubber and the like.

Moreover, it is preferable that the rubber ingredient is at least one of natural rubber and synthetic isoprene rubber in an amount of not less than 50% by weight from a viewpoint of adhesion property and fracture property of rubber.

When the metal salt of the organic acid is included as the component of the adhesion promoter composition, it is preferable to be in the amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid based on 100 g of the rubber ingredient. When it is less than 2.0×10⁻⁴ mole, the desired effects may not be obtained, while when it exceeds 2.0×10⁻² mole, the desired effect is not further improved and the cost becomes higher.

Additionally, for the same reasons, the amount is more preferably 4.0×10⁻⁴ 1.0×10⁻² mole, further more preferably 1.0×10⁻³ -4.0×10⁻³ mole.

Further, when the hydrous inorganic salt is included as the component of the adhesion promoter composition, it is preferably 2.5×10⁻³ -2.5×10⁻¹ mole calculated in terms of water in the hydrous inorganic salt based on 100 g of the rubber ingredient. When it is less than 2.5×10⁻³ mole, the desired effect may not be obtained, while when it exceeds 2.5×10⁻¹ mole, the desired effect is not further improved, rather the water content becomes too large and the adhesion property may be lowered.

Additionally, for the same reasons the amount is preferably 5.0×10⁻³ -2.0×10⁻¹ mole, further more preferably 7.5×10⁻³ -7.5×10⁻² mole.

Furthermore, when the organic molybdenum compound is the component of the adhesion promoter composition, it is preferably added in the amount of 2.0×10⁻⁶ -2.0×10 mole calculated in terms of molybdenum in the organic molybdenum compound based on 100 g of the rubber ingredient. When it is less than 2.0×10⁻⁶ mole, the desired effect may not be obtained, while when it exceeds 2.0×10 mole, the desired effect is not further improved, and the cost becomes higher.

Additionally, for the same reasons, the amount is more preferably 2.0×10⁻⁵ -2.0×10⁻² mole, further more preferably 1.0×10⁻⁴ -1.0×10⁻³ mole.

Further, sulfur is preferably added in the amount of 3-8 g based on 100 g of the rubber ingredient. When it is less than 3 g, sulfur can not be supplied in an amount sufficient to form Cu_(x) S as a source of developing adhesive force and hence the adhesive force is lowered, while when it exceeds 8 g, Cu_(X) S is excessively formed and agglomeration fracture of enlarged Cu_(x) S is created which lowers the adhesive force and further the resistance to thermal aging of the rubber composition is lowered.

Additives usually used in the rubber industry may be compounded in their usual amounts in addition to the above components in the invention.

For example, a filler such as carbon black, silica or the like; a softening agent such as aromatic oil or the like; a vulcanization accelerator, for example, guanidines such as diphenylguanidine or the like, thiazoles such as mercaptobenzothiazole or the like, sulfenamides such as N,N'-dicyclohexyl-2-benzothiazolylsulfenamide or the like, thiurams such as tetramethyithiuram disulfide or the like; an accelerator activator such as zinc oxide or the like; and an antioxidant, for example, poly(2,2,4-trimethyl-l, 2-dihydroquinoline), amines such as phenyl-α-naphthylamine or the like may be added.

Among them, the filler such as carbon black, silica or the like is known as a reinforcing agent for increasing a tensile strength, a strength at rupture, a modulus of elasticity, a hardness and the like of a vulcanized rubber, and improving a wear resistance, a resistance to stretching and the like thereof. Zinc oxide forms a complex compound with a fatty acid and is known as an accelerator activator for enhancing the vulcanization acceleration.

Furthermore, it is preferable that the steel cord to be adhered with the adherent rubber composition according to the invention is subjected to plating with a brass, zinc, or an alloy containing nickel or cobalt therewith for improving the adhesion to rubber, and more preferably to brass plating treatment. A good and stable adhesion is obtained when the Cu content in the brass plating for the steel cord is not more than 75% by weight, preferably 55-70% by weight.

The twisting structure of the cord is not limited particularly.

Further, the production of the adhesion promoter composition according to the invention and the production of the adherent rubber composition containing the adherent promoter composition are carried out in the usual manner.

EXAMPLES

The invention will be described with reference to the examples and comparative examples below.

A rubber composition is prepared according to the compounding recipe described in each table, and further a cord-reinforced rubber is prepared as mentioned later, and tests are conducted by the following methods to obtain results as shown in the same tables.

Table 1 illustrates the effect when the adhesion promoter composition contains a metal salt of an organic acid and a hydrous inorganic salt. Table 2 illustrates the effect when the adhesion promoter composition contains a metal salt of an organic acid and an organic molybdenum compound. Each of Tables 3-6 illustrates the effect when the adhesion promoter composition contains a metal salt of an organic acid, a hydrous inorganic salt and an organic molybdenum compound.

Since the adhesion property is dependent upon the season, the weather and the like, if the day of kneading rubber differs even in the same compounding recipe, the adhesion property may differ. Therefore, in the examples, the day of kneading rubber is same every each table.

Examples 28 and 29 described in Table 3 illustrate the case of previously compounding a metal salt of an organic acid and an organic molybdenum compound, respectively.

(1) Tensile test

After a sample is prepared by vulcanizing each of the rubber composition under condition of 160° C.×20 minutes, it is subjected to a tensile test according to JIS K 6301 to measure a tensile stress at 100% elongation (M₁₀₀) and an elongation at breakage (E_(B)).

(2) Adhesion test

Steel cords (1×5 twisting structure, filament diameter: 0.25 mm) subjected to brass plating (Cu: 63% by weight, Zn: 37% by weight) are arranged side, by side at an interval of 12.5 mm and coated from both sides with each of the rubber compositions and vulcanized under conditions of 160° C.×20 minutes to form a sample of 12.5 mm in thickness, from which a steel cord is pulled out under the following conditions according to ASTM-D-2229 to measure a pulling force. With respect to each of initial adhesion property and adhesion property in aging under the presence of oxygen, the measured value is represented by an index on the basis that each control is 100. The larger the index value, the better the property.

Initial adhesion property

The measurement is carried out just after the above vulcanization.

Adhesion property in aging under the presence of oxygen

After the vulcanization, each sample is aged in air at 120° C. for 7 days for the measurement.

                                      TABLE 1                                      __________________________________________________________________________                                  Compar-                                              ative                                                                         Example Example Example                                                                    1  2  3  4  5  1  2* 6  7                                        __________________________________________________________________________     Compound recipe (g)                                                              Natural rubber 100 100 100 100 100 100 100 100 100                             Carbon black 60 60 60 60 60 60 60 60 60                                        Zinc oxide 8 8 8 8 8 8 8 8 8                                                   Antioxidant 2 2 2 2 2 2 2 2 2                                                  Vulcanization accelerator 1 1 1 1 1 1 1 1 1                                    Sulfur 5 5 5 5 5 5 5 5 5                                                       Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.8 0.8 0.8 3 7 --  -- 0.8 0.8                               Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O 1 3 7 1 1 -- -- -- --                     Na.sub.2 SiO.sub.3.9H.sub.2 O -- -- -- -- -- -- -- 1 --                        Na.sub.2 B.sub.6 O.sub.7.10H.sub.2 O -- -- -- -- -- -- -- -- 1                 Adhesion promoter -- -- -- -- -- -- 0.7 -- --                                  for comparison                                                                 H.sub.2 O/Me (molar ratio) 9.0 26.9 62.8 2.4 1.0 -- -- 12.8 10.4                                                    Tensile test                              M.sub.100 (MPa) 5.3 5.3 5.5 5.6 5.4 4.6 5.8 5.6 4.9                            E.sub.B (%) 331 330 328 324 329 334 301 300 326                                Adhesion test                                                                  Initial adhesion property 106 106 106 112 106 94 100 112 106                   (index)                                                                        Adhesion property in aging 163 125 123 150 110 110 100 175 150                 under the presence of oxygen                                                   (index)                                                                      __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________                                 Comparative                                          Example Example                                                                              11 12 13 14 11 12 13*                                          __________________________________________________________________________     Compound recipe (g)                                                              Natural rubber 100 100 100 100 100 100 100                                     Carbon black 50 50 50 50 50 50 50                                              Zinc oxide 8 8 8 8 8 8 8                                                       Antioxidant 2 2 2 2 2 2 2                                                      Vulcanization accelerator 1 1 1 1 1 1 1                                        Sulfur 5 5 5 5 5 5 5                                                           Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.9 0.9 0.9 0.9 --  0.9 --                                   Molybdenum -- -- 0.3 -- -- --                                                  neodecanoate                                                                   Molybdenum 0.3 0.6 -- -- -- -- --                                              naphthenate                                                                    Mo-DTP -- -- -- 0.3 -- -- --                                                   Cobalt neodecanoate -- -- -- -- -- -- 1.2                                      Mo/Me (molar ratio) 0.20 0.40 0.29 0.21 -- -- --                               Tensile test                                                                   M.sub.100 (MPa) 4.8 5.1 4.9 5.1 2.5 4.7 5.0                                    E.sub.B (%) 420 409 423 403 375 425 400                                        Adhesion test                                                                  Initial adhesion property 105 105 105 100 11 33 100                            (index)                                                                        Adhesion property in aging under 130 145 120 120 100 100 100                   the presence of oxygen (index)                                               __________________________________________________________________________

                                      TABLE 3                                      __________________________________________________________________________                                                    Compar-                            ative                                                                         Example Example                                                                            21 22 23 24 25 26 27 28 29 30 31 21 22*                          __________________________________________________________________________     Compounding recipe (g)                                                           Natural rubber 100 100 100 100 100 100 100 100 100 100 100 100 100                                                              Carbon black 60 60 60                                                         60 60 60 60 60 60 60 60                                                        60 60                          Zinc oxide 8 8 8 8 8 8 8 8 8 8 8 8 8                                           Antioxidant 2 2 2 2 2 2 2 2 2 2 2 2 2                                          Vulcanization accelerator 1 1 1 1 1 1 1 1 1 1 1 1 1                            Sulfur 5 5 5 5 5 5 5 5 5 5 5 5 5                                               Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.9 0.9 0.9 0.9 3 5 0.9 0.72 0.79 0.9 0.9 --  --                                                              Molybdenum naphthenate                                                        0.05 0.3 0.9 5 1 2 --                                                          0.28 -- 0.3 0.3 -- --                                                           Mo--DTP -- -- -- -- --                                                        -- 0.3 -- 0.31 -- -- --                                                        --                             Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O 1 1 1 1 1 1 1 1 1 3 7 -- --                                                                Adhesion promoter for                                                         -- -- -- -- -- -- -- --                                                        -- -- -- -- 0.7                                                                 comparison                    H.sub.2 O/Me (molar ratio) 9.3 9.3 9.3 9.3 3.1 1.9 9.3 11.8 10.4 28.2                                                          65.4 -- --                     Mo/Me (molar ratio) 0.03 0.20 0.61 3.4 0.22 0.27 0.02 0.24 0.24 0.20                                                           0.20 -- --                     Tensile test                                                                   M.sub.100 (MPa) 3.2 3.2 3.4 3.5 3.6 3.9 3.8 3.2 3.5 3.7 3.8 3.4 4.3                                                             E.sub.B (%) 434 426                                                           428 424 420 416 392 449                                                        426 425 423 442 415                                                             Adhesion test                 Initial adhesion property 108 121 121 121 121 115 100 121 107 121 100                                                          29 100                         (index)                                                                        Adhesion property in aging 105 125 125 113 113 105 113 113 125 113 113                                                         78 100                         under the presence of                                                          oxygen (index)                                                               __________________________________________________________________________

                  TABLE 4                                                          ______________________________________                                                                   Compar-                                                 ative                                                                         Example Example                                                                            41   42      43     41    42*                                    ______________________________________                                         Compounding recipe (g)                                                           Natural rubber 100 100 100 100 100                                             Carbon black 60 60 60 60 60                                                    Zinc oxide 8 8 8 8 8                                                           Antioxidant 2 2 2 2 2                                                          Vulcanization 1 1 1 1 1                                                        accelerator                                                                    Sulfur 5 5 5 5 5                                                               Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.9 0.9 3 --  --                                             Molybdenum naphthanate 0.3 3 0.3 -- --                                         Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O 1 1 1 -- --                               Adhesion promoter for -- -- -- -- 0.7                                          comparison                                                                     H.sub.2 O/Me (molar ratio) 7.9 7.9 2.6  --                                     Mo/Me (molar ratio) 0.20 2.05 0.07 -- --                                       Tensile test                                                                   M.sub.100 (MPa) 5.2 5.5 5.5 4.6 5.8                                            E.sub.B (%) 316 325 331 334 301                                                Adhesion test                                                                  Initial adhesion 129 121 114 86 100                                            property (index)                                                               Adhesion property in 162 155 143 60 100                                        aging under the presence                                                       presence of oxygen                                                             (index)                                                                      ______________________________________                                    

                                      TABLE 5                                      __________________________________________________________________________                                     Compar-                                           ative                                                                         Example Example Example                                                                       51 52 53 54 55 51*  56                                        __________________________________________________________________________     Compounding recipe (g)                                                           Natural rubber 100 100 100 100 100 100 70 (NR)                                        30 (SBR)                                                                Carbon black 60 60 60 60 60 60 60                                              Zinc oxide 8 8 8 8 8 8 8                                                       Antioxidant 2 2 2 2 2 2 2                                                      Vulcanization accelerator 1 1 1 1 1 1 1                                        Sulfur 5 5 5 5 5 5 5                                                           Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.8 --  -- -- -- -- 0.8                                      Zinc naphthenate -- 0.9 0.9 -- -- -- --                                        Zinc rosinate -- -- -- 1.8 -- -- --                                            Zinc salt of tall oil -- -- -- -- 1.4 -- --                                    acid                                                                           Molybdenum neodecanoate -- -- 1.0 -- -- -- --                                  Molybdenum naphthenate 0.2 0.2 -- 0.2 0.2 -- 0.2                               Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O 1.0 1.0 1.0 1.0 1.0 -- 1.0                                                    Adhesion promoter for comparison --                                           -- -- -- -- 0.7 --                          H.sub.2 O/Me (molar ratio) 9.0 9.3 8.3 9.0 8.6 -- 10.2                         Mo/Me (molar ratio) 0.15 0.16 0.14 0.15 0.15 -- 0.17                           Tensile test                                                                   M.sub.100 (MPa) 5.3 5.2 5.3 5.2 5.6 5.7 5.5                                    E.sub.B (%) 324 330 321 350 320 307 310                                        Adhesion test                                                                  Initial adhesion property (index) 135 115 135 130 145 100 100                  Adhesion property in aging under 170 170 120 120 190 100 175                   the presence of oxygen (index)                                               __________________________________________________________________________

                  TABLE 6                                                          ______________________________________                                                                     Compar-                                               ative                                                                         Example Example                                                                         61   62     63     64   65   61*                                    ______________________________________                                         Compounding recipe (g)                                                           Natural rubber 100 100 100 100 100 100                                         Carbon black 60 60 60 60 60 60                                                 Zinc oxide 8 8 8 8 8 8                                                         Antioxidant 2 2 2 2 2 2                                                        Vulcanization 1 1 1 1 1 1                                                      accelerator                                                                    Sulfur 5 5 5 5 5 5                                                             Adhesion promoter                                                              composition                                                                    Zinc neodecanoate 0.8 --  -- -- -- --                                          Aluminum neo- -- 1.0 -- -- -- --                                               decanoate                                                                      Titanium neo- -- -- 1.0 -- -- --                                               decanoate                                                                      Potassium neo- -- -- -- 0.7 -- --                                              decanoate                                                                      Zirconium neo- -- -- -- -- 1.0 --                                              decanoate                                                                      Molybdenum 0.2 0.2 0.2 0.2 0.2 --                                              naphthenate                                                                    Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O 1.0 1.0 1.0 1.0 1.0 --                    Adhesion promoter -- -- -- -- -- 0.7                                           for comparison                                                                 H.sub.2 O/Me 9.0 9.7 8.6 7.4 9.0 --                                            (molar ratio)                                                                  Mo/Me 0.15 0.16 0.15 0.12 0.15 --                                              (molar ratio)                                                                  Tensile test                                                                   M.sub.100 (MPa) 4.1 3.8 3.6 4.0 3.4 4.2                                        E.sub.B (%) 427 395 418 415 418 412                                            Adhesion text                                                                  Initial adhesion 135 126 135 135 116 100                                       property (index)                                                               Adhesion property in 170 135 122 131 115 100                                   aging under the                                                                presence of                                                                    oxygen (index)                                                               ______________________________________                                    

Natural rubber: RSS#4, trade name, made by Tech Behung Co,, Ltd.

SBR: Toughden 2000R, trade name, made by Asahi Chemical Industry Co., Ltd. (used in only Example 57)

Carbon black: N330 (N326 is used in only a compounding recipe of Table 6)

Antioxidant: Nocrac 6C, trade name, made by Ohuchi Shinko Kagaku Kogyo Co-, Ltd.

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene diamine

Vulcanization accelerator: Nocceler DZ, trade name, made by Ohuchi Shinko Kagaku Kogyo Co., Ltd

N,N'-dicyclohexyle-2-benzothiazolyl sulfenamide

Adhesion promoter for comparison: Manobond C22.5, trade name, made by Rhone-Poulenc Viscosuisse SA.

* mark: This mark shows a control in each table when each of the initial adhesion property and the adhesion property in aging under the presence of oxygen is represented by an index.

Furthermore, a ratio of an effective component (metal) in the metal salt of organic acid or the organic molybdenum compound used in each table is shown in Table 7. In this case, ◯ mark corresponds to Example 28 and ⊚ mark Example 29, respectively.

                  TABLE 7                                                          ______________________________________                                                            Effective component                                           Compound (% bye weight)                                                      ______________________________________                                         Zinc neodecanoate  20.4                                                          Molybdenum naphthenate 18.2                                                    Zinc naphthenate 17.6                                                          Zinc rosinate 8.9                                                              Zinc salt of tall oil acid 12.3                                                Aluminum neodecanoate 6.3                                                      Titanium neodecanoate 12.5                                                     Potassium neodecanoate 17.0                                                    Zirconium neodecanoate 22.7                                                    Cobalt neodecanoate 14.2                                                       Molybdenum neodecanoate 25.9                                                   Mo--DTP 19.1                                                                   ∘ Zinc neodecanoate/ (Zn)12.3 (Mo)4.3                              Molybedenum naphthenoate                                                       ⊚ Zinc neodecanoate/Mo--DTP (Zn)13.4 (Mo)4.92                 ______________________________________                                    

As seen from Table 1, when the metal salt of organic acid and the hydrous inorganic salt are included, both the initial adhesion property and the adhesion property in aging under the presence of oxygen are improved. And also, the effect is observed even when the kind of the hydrous inorganic salt is varied.

As seen from Table 2, when the metal salt of organic acid and the organic molybdenum compound are included, the initial adhesion property and the adhesion property in aging under the presence of oxygen, particularly the latter property are improved. Moreover, the effect is observed irrespectively of the kind of the organic molybdenum compound.

As seen from Table 3, when the metal salt of organic acid, the hydrous inorganic salt and the organic molybdenum compound are included, both the initial adhesion property and the adhesion property in aging under the presence of oxygen are effectively improved The effect is observed irrespectively of the molar ratio of H₂ O/Me and the molar ratio of Mo/Me.

As seen from Table 4, a considerable improvement of the desired effect is obtained when the metal salt of organic acid, the hydrous inorganic salt and the organic molybdenum compound are included--

As seen from Table 5, the desired effect is observed irrespectively of the kind of the organic acid constituting the metal salt of organic acid and of the organic molybdenum compound.

As seen from Table 6, the desired effect is observed irrespectively of the kind of the metal constituting the metal salt of organic acid.

As seen from the above, each of examples has a stable adhesion property on a high level without degradation of rubber properties.

INDUSTRIAL APPLICABILITY

The metal salts of organic acid except for cobalt have not been put into practical use because the adhesive force just after vulcanization is poor. According to the invention, however, when a specified metal salt of organic acid except for cobalt is used, in combination with the hydrous inorganic salt or the organic molybdenum compound, is obtained an adhesion promoter composition improved in safety and economy concerns and also having an improved adhesive force Likewise, the adherent rubber composition containing the adhesion promoter is similarly improved.

Furthermore, a higher initial adhesive force is obtained by adding the hydrous inorganic salt and the organic molybdenum compound to the specified metal salt of organic acid according to the invention, and can stably be maintained.

Therefore, the invention can particularly be applied for adhesion promotion between a steel cord subjected to brass plating and the rubber for coating the steel cord. 

We claim:
 1. An adhesion promoter composition comprisinga metal salt of an organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and a hydrous inorganic salt.
 2. An adhesion promoter composition comprisinga metal salt of an organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and an organic molybdenum compound.
 3. The adhesion promoter composition according to claim 1, further comprising an organic molybdenum compound.
 4. The adhesion promoter composition according to claim 1, wherein a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100.
 5. The adhesion promoter composition according to claim 3, wherein a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100.
 6. The adhesion promoter composition according to claim 3, wherein a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100, and a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100, and a molar ratio (H₂ O/Mo) of water (H₂ O) in the hydrous inorganic salt to molybdenum (Mo) in the organic molybdenum compound is 1-500.
 7. The adhesion promoter composition according to claim 3, wherein a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid is 0.1-100.
 8. The adhesion promoter composition according to claim 2, wherein a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100.
 9. An adherent rubber composition characterized by compounding at least:a) at least one rubber ingredient selected from the group consisting of natural rubber and synthetic rubbers, b) an adhesion promoter composition comprisinga metal salt of an organic acid containing at least one metal selected from the group consisting of Zn, K, Al, Ti and Zr, and an organic molybdenum compound, and c) sulfur.
 10. The adherent rubber composition according to claim 9, wherein the adhesion promoter composition comprises a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid of 0.01-100.
 11. An adherent rubber composition characterized by compounding at least:a) at least one rubber ingredient selected from the group consisting of natural rubber and synthetic rubbers, b) an adhesion promoter composition comprisinga metal salt of an organic acid containing at least one metal selected from the group consisting of Zn. K. Al, Ti and Zr, and a hydrous inorganic salt, and c) sulfur.
 12. The adherent rubber composition according to claim 11, wherein the adhesion promoter composition further comprises an organic molybdenum compound.
 13. The adherent rubber composition according to claim 11, wherein the adhesion promoter composition comprises a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid of 0.1-100.
 14. The adherent rubber composition according to claim 12, wherein the adhesion promoter composition comprises a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid of 0.1-100.
 15. The adherent rubber composition according to claim 12, wherein the adhesion promoter composition comprises a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid of 0.01-100.
 16. The adherent rubber composition according to claim 12, wherein the adhesion promoter composition comprises a molar ratio (H₂ O/Me) of water (H₂ O) in the hydrous inorganic salt to metal (Me) in the metal salt of the organic acid of 0.1 to 100, and a molar ratio (Mo/Me) of molybdenum (Mo) in the organic molybdenum compound to metal (Me) in the metal salt of the organic acid is 0.01-100, and a molar ratio (H₂ O/Mo) of water (H₂ O) in the hydrous inorganic salt to molybdenum (Mo) in the organic molybdenum compound is 1-500.
 17. The adherent rubber composition according to claims 11, 13, or 14, wherein the adhesion promoter composition is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.5×10⁻³ -2.5×10⁻¹ mole calculated in terms of water in the hydrous inorganic salt, and the sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient.
 18. The adherent rubber composition according to claims 15, 9 or 10; wherein the adhesion promoter composition is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.0×10⁻⁶ -2.0×10 mole calculated in terms of molybdenum in the organic molybdenum compound, and the sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient.
 19. The adherent rubber composition according to claims 12 or 16, wherein the adhesion promoter composition is compounded in an amount of 2.0×10⁻⁴ -2.0×10⁻² mole calculated in terms of metal in the metal salt of the organic acid and in an amount of 2.5×10⁻³ -2.5×10⁻¹ mole calculated in terms of water in the hydrous inorganic salt and in an amount of 2.0×10⁻⁶ -2.0×10 mole calculated in terms of molybdenum in the organic molybdenum compound, and the sulfur is compounded in an amount of 3-8 g, based on 100 g of the rubber ingredient. 